bugfix: Multiple battle plans are now always applied correctly

[Stubbjax]

Closes #46
Closes #2209

This change fixes an issue where multiple Strategy Center battle plans are not correctly applied. The issue is that only the most recent plan is applied, as only the new plan data is passed to the battle plan application logic.

For example, in retail, if the player has Search and Destroy on one Strategy Center, and then selects Bombardment on another, the data that gets applied to all units becomes:

Search and Destroy: 0 (this undoes the range bonus)
Bombardment: 1 (new bonus is applied)
Hold the Line: 0

After this change, the logic correctly accounts for existing plans, and so the data becomes this:

Search and Destroy: 1 (range bonus remains intact)
Bombardment: 1 (new bonus is applied)
Hold the Line: 0

In the Player::applyBattlePlanBonusesForPlayerObjects method, the bonus is essentially the delta, while m_battlePlanBonuses is the combined bonus. The problem was that the bonus was being applied to units instead of m_battlePlanBonuses. However, the armour scalar is still expected as a delta when being applied to units, so a temporary newBonus is now used to merge the armour scalar delta with the combined bonus.

[greptile-apps]

Greptile Overview

Greptile Summary

Fixed a critical bug where multiple Strategy Center battle plans would not stack correctly - only the most recently activated plan would remain active while previous plans were incorrectly cleared.

The issue occurred in Player::applyBattlePlanBonusesForPlayerObjects where the function correctly accumulated all bonuses in m_battlePlanBonuses but then applied only the delta bonus parameter to existing units. Since the delta contains zeroes for non-active bonuses in the specific activation, this caused weapon bonus flags (searchAndDestroy, bombardment, holdTheLine) to be incorrectly cleared on units when a second plan was activated.

The fix creates a temporary newBonus object that combines the accumulated bonuses from m_battlePlanBonuses with the delta armor scalar from bonus. This ensures:

• Weapon bonus flags remain set for all active plans (using accumulated values)
• Sight range scalar uses the accumulated total (for absolute recalculation)
• Armor scalar uses the delta (for multiplicative application via applyDamageScalar)

The change is properly guarded by RETAIL_COMPATIBLE_CRC to maintain compatibility with the original game behavior.

Confidence Score: 5/5

• This PR is safe to merge - it fixes a well-understood bug with a clean, minimal solution
• The fix correctly addresses the root cause by applying accumulated bonuses instead of deltas for flags/absolute values while preserving delta application for multiplicative values. The logic is sound, the change is minimal and well-isolated behind a feature flag, and applies identically to both game versions.
• No files require special attention

Important Files Changed

Filename	Overview
Generals/Code/GameEngine/Source/Common/RTS/Player.cpp	Fixed battle plan bonus application to use accumulated bonuses instead of just deltas, preserving all active plans
GeneralsMD/Code/GameEngine/Source/Common/RTS/Player.cpp	Fixed battle plan bonus application to use accumulated bonuses instead of just deltas, preserving all active plans

Sequence Diagram

sequenceDiagram
    participant SC1 as Strategy Center 1
    participant SC2 as Strategy Center 2
    participant Player as Player
    participant Units as Player Units
    
    Note over SC1,Units: First Battle Plan Activation
    SC1->>Player: Activate Search & Destroy<br/>(bonus delta)
    Player->>Player: m_battlePlanBonuses = bonus<br/>searchAndDestroy=1, bombardment=0
    Player->>Units: Apply bonuses to all units<br/>(searchAndDestroy flag set)
    
    Note over SC1,Units: Second Battle Plan Activation (Bug Scenario)
    SC2->>Player: Activate Bombardment<br/>(bonus delta: bombardment=1, searchAndDestroy=0)
    Player->>Player: m_battlePlanBonuses updated<br/>searchAndDestroy=1, bombardment=1
    
    alt OLD CODE (Bug)
        Player->>Units: iterateObjects(bonus)<br/>(searchAndDestroy=0, bombardment=1)
        Note over Units: BUG: searchAndDestroy flag cleared!<br/>Only bombardment remains active
    else NEW CODE (Fixed)
        Player->>Player: newBonus = m_battlePlanBonuses<br/>newBonus.armorScalar = bonus.armorScalar
        Player->>Units: iterateObjects(newBonus)<br/>(searchAndDestroy=1, bombardment=1)
        Note over Units: FIXED: Both plans remain active
    end

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